This is a reference to Jaʿfar al-Ṣādiq's use of term Āl Umayya rather than the more common term Banū Umayya to refer to the Umayyads. Hossein Modarressi draws on this reference to make the case that al-Ṣādiq's advice to his followers to follow that which contradicts the masses had no sectarian implications; rather, it was because the Umayyads had insisted on promoting beliefs and practices that explicitly contradicted the legal legacy of the House of the Prophet.
This source is part of the Online Companion to Hossein Modarressi, Text and Interpretation: Imam Jaʿfar al-Ṣādiq and His Legacy in Islamic Law (Harvard University Press, 2022).